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  <div class="section" id="module-pydoc">
<h1>26.1. <tt class="xref docutils literal"><span class="pre">pydoc</span></tt> &#8212; Documentation generator and online help system<a class="headerlink" href="#module-pydoc" title="Permalink to this headline">¶</a></h1>
<p>
<span class="versionmodified">New in version 2.1.</span></p>
<p id="index-493">The <tt class="xref docutils literal"><span class="pre">pydoc</span></tt> module automatically generates documentation from Python
modules.  The documentation can be presented as pages of text on the console,
served to a Web browser, or saved to HTML files.</p>
<p>The built-in function <a title="help" class="reference external" href="functions.html#help"><tt class="xref docutils literal"><span class="pre">help()</span></tt></a> invokes the online help system in the
interactive interpreter, which uses <tt class="xref docutils literal"><span class="pre">pydoc</span></tt> to generate its documentation
as text on the console.  The same text documentation can also be viewed from
outside the Python interpreter by running <strong>pydoc</strong> as a script at the
operating system&#8217;s command prompt. For example, running</p>
<div class="highlight-python"><pre>pydoc sys</pre>
</div>
<p>at a shell prompt will display documentation on the <a title="Access system-specific parameters and functions." class="reference external" href="sys.html#module-sys"><tt class="xref docutils literal"><span class="pre">sys</span></tt></a> module, in a
style similar to the manual pages shown by the Unix <strong>man</strong> command.  The
argument to <strong>pydoc</strong> can be the name of a function, module, or package,
or a dotted reference to a class, method, or function within a module or module
in a package.  If the argument to <strong>pydoc</strong> looks like a path (that is,
it contains the path separator for your operating system, such as a slash in
Unix), and refers to an existing Python source file, then documentation is
produced for that file.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">In order to find objects and their documentation, <tt class="xref docutils literal"><span class="pre">pydoc</span></tt> imports the
module(s) to be documented.  Therefore, any code on module level will be
executed on that occasion.  Use an <tt class="docutils literal"><span class="pre">if</span> <span class="pre">__name__</span> <span class="pre">==</span> <span class="pre">'__main__':</span></tt> guard to
only execute code when a file is invoked as a script and not just imported.</p>
</div>
<p>Specifying a <em class="xref">-w</em> flag before the argument will cause HTML documentation
to be written out to a file in the current directory, instead of displaying text
on the console.</p>
<p>Specifying a <em class="xref">-k</em> flag before the argument will search the synopsis
lines of all available modules for the keyword given as the argument, again in a
manner similar to the Unix <strong>man</strong> command.  The synopsis line of a
module is the first line of its documentation string.</p>
<p>You can also use <strong>pydoc</strong> to start an HTTP server on the local machine
that will serve documentation to visiting Web browsers. <strong>pydoc</strong>
<em class="xref">-p 1234</em> will start a HTTP server on port 1234, allowing you to browse
the documentation at <tt class="docutils literal"><span class="pre">http://localhost:1234/</span></tt> in your preferred Web browser.
<strong>pydoc</strong> <em class="xref">-g</em> will start the server and additionally bring up a
small <a title="Interface to Tcl/Tk for graphical user interfaces" class="reference external" href="tkinter.html#module-Tkinter"><tt class="xref docutils literal"><span class="pre">Tkinter</span></tt></a>-based graphical interface to help you search for
documentation pages.</p>
<p>When <strong>pydoc</strong> generates documentation, it uses the current environment
and path to locate modules.  Thus, invoking <strong>pydoc</strong> <em class="xref">spam</em>
documents precisely the version of the module you would get if you started the
Python interpreter and typed <tt class="docutils literal"><span class="pre">import</span> <span class="pre">spam</span></tt>.</p>
<p>Module docs for core modules are assumed to reside in
<a class="reference external" href="http://docs.python.org/library/">http://docs.python.org/library/</a>.  This can be overridden by setting the
<span class="target" id="index-494"></span><strong class="xref">PYTHONDOCS</strong> environment variable to a different URL or to a local
directory containing the Library Reference Manual pages.</p>
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